1) Field of the Invention
This invention relates generally to fabrication of a semiconductor device and more particularly to a carrier and assembly method for ball grid array packages that replace manual flipping of ball grid array substrates during assembly with flipping the carrier.
2) Description of the Prior Art
Conventionally, Auer boats by Auer Precision Co., Inc. of Mesa, Ariz., are used to hold substrates during processing of ball grid array packages, such as FEBGA and EBGA. Substrates for the ball grid array packages are placed in an Auer boat prior to die attach. The substrates are manually flipped prior to marking. They are manually flipped again prior to ball attach. The manual flipping steps are time consuming, typically requiring 30 to 35 minutes per 200 unit lot. Also, the manual handling operations are a significant cause of quality problems, such as handling damage, electrostatic discharge, and misalignment.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following patents.
U.S. Pat. No. 5,695,331 (Nutter) shows a multiple width boat carrier. The carrier is adjustable to accommodate various size IC boats.
U.S. Pat. No. 5,843,808 (Karnezos) shows a method for handling TAB grid arrays using a part of the package known as a stiffener as a carrier during assembly.